/*
 * Copyright (c) 2014, Ege University
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the
 *   distribution.
 * - Neither the name of the copyright holder nor the names of
 *   its contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * @author Kasım Sinan YILDIRIM (sinanyil81@gmail.com)
 *
 * Made use of the source code of JProwler simulator 
 * (http://w3.isis.vanderbilt.edu/projects/nest/jprowler/)
 * 
 */

/*
 * Copyright (c) 2003, Vanderbilt University
 * All rights reserved.
 *
 * 
 * IN NO EVENT SHALL THE VANDERBILT UNIVERSITY BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE VANDERBILT
 * UNIVERSITY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * THE VANDERBILT UNIVERSITY SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE VANDERBILT UNIVERSITY HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 */

package simit.hardware.transceiver;

import simit.statistics.GaussianDistribution;

public class RadioSignal {

	public static double fallingFactorHalf = 1.1;
//	public static double staticRandomFactor = 0.3;
	public static double staticRandomFactor = 0.0;
	public static double radioStrengthCutoff = 0.1;
	public static double dynamicRandomFactor = 0.05;

	public static double noiseVariance = 0.025;
	public static double maxAllowedNoiseOnSending = 5;
	public static double receivingStartSNR = 4.0;
	public static double corruptionSNR = 2.0;

	public static double getStaticFading(double distanceSquare,
			double maxSignalStrength) {
		double staticRandomFading = 1.0 + staticRandomFactor
				* GaussianDistribution.nextGaussian();

		return staticRandomFading <= 0.0 ? 0.0 : maxSignalStrength
				* staticRandomFading
				/ (1.0 + Math.pow(distanceSquare, fallingFactorHalf));
	}

	public static double getDynamicStrength(double staticFading) {
		double dynamicRandomFading = 1.0 + dynamicRandomFactor
				* GaussianDistribution.nextGaussian();
		return dynamicRandomFading <= 0.0 ? 0.0 : staticFading* dynamicRandomFading;
	}

	public static boolean isChannelFree(double noiseStrength) {
		return noiseStrength < maxAllowedNoiseOnSending * noiseVariance;
	}

	public static boolean isCorrupted(double signalStrength, double noiseStrength) {
		return calcSNR(signalStrength, noiseStrength) < corruptionSNR;
	}

	protected static double calcSNR(double signalStrength, double noiseStrength) {
		return signalStrength / (noiseVariance + noiseStrength);
	}

	public static boolean isReceivable(double signalStrength, double noiseStrength) {
		return calcSNR(signalStrength, noiseStrength) > receivingStartSNR;
	}
}
